Sci fi treat from 1953. One night, young David McLean sees a spaceship crash into a nearby sandpit. His father goes to investigate but comes back changed. Where once he was cheerful and affectionate, he's now sullen and rude. Others fall into the sandpit and begin acting like him: cold, ill-tempered and conspiratorial. David knows that aliens are taking over the bodies of humans, but he'll soon discover there have been far more of these terrible thefts than he could have imagined.